Ionization type gas flowmeter



Feb. 3, 1953 A. A. QBEPMAIER IoNIzATIoN TYPE GAsPFLowMETER Filed Nov. 12, 1947 ww mSQ Si NQ Patented Feb. 3, 195.3

UNITED STATES cargar OFFICE N IONIZATON TYPE GAS FLOWIVIETER Application November 12, 1947, Serial No. 785,239

1 Claim. 1

My invention relates, generally, to gas now measuring means and it h-as particular'relation to such means which determines the velocity of flow .by ionizing molecules of the gas.

Among the objects of my invention are: To ionize molecules of the gas whose velocity is to be measured in an electric field acting transversely of the direction of gas ow; to measure the resultant current flow; to maintain a .pair of spaced electrodes between which the gas ows at a predetermined potential and to ionize molecu-les of the gas in the space between the electrodes; to measure the current now between the electrodes which is the result of the combined actions of the potential therebetween and the velocity of the gas; and to employ thermionic means for measuring the current flow.

Other objects of my invention will, in part, be obvious and in part appear hereinafter.

My invention is disclosed in the embodiment thereof sh-own in the accompanying drawing and it comprises the features of construction, combination of elements, arrangement of parts, and method of operation which will be exemplified in the construction and meth-od set forth hereinafter and the sco-pe of the application of which will be indicated in the appended claim.

For a more complete understanding of the nature and scope of my invention reference can be had to the following detailed description talren together with the accompanying drawing in which the single figure illustrates, diagrammatically, a preferred embodiment of my invention and method of practicing the same.

Referring now to the drawing it will be noted that the reference character 9 designates a conduit in which gas iiows as indicated by an arrow Si! the velocity of which is to be measured. The gas is arranged to iiow between an electrode or plate II and another electrode or grid I2 which are maintained at a predetermined relative direct potential by connection to terminals i3 and Ill which, as shown, are connected to a suitable source of direct po-tential, such as a potential of Iii volts. The molecules of the gas flowing between the electro-des II and I2 are indicated at I5. These molecules I5 are bombarded or ionized by alpha particles, indicated at IS, which are emitted from a radioactive foil o-r source Il' through the openings in the electrode or grid I2. The resultant ionized molecules or particles have mass and they are moved in a direction which is a result of the combined actions of the velocity of the gas iiow and the potential that is maintained between the electrodes II and I2.

The resultant velocity of the ionized molecules I5 of the gas due to the combined actions of the gas velocity and the transversely acting electri-c field .maintained between the electrodes I I an-d I2 may be stated:

Vr=resultant velocity Vp=velocity due to potential Vg=velocity of the gas Now, in time t an ion 15 moves a Idistance d in a direction making an angle a with the electrode or plate I I. This `may be stated:

in the same time an ion I5 moves parallel to the electrode o-r plate II -a distance d. This may be stated:

From the foregoing it will .be noted that all of the ionized molecules I5 do not reach the electrode or plate II. Some of them are blown completely out of the electric field that is maintained between the electrodes II an-d I2 by the flow of gas therebetween. Since theradioactive material Il continuously emits alpha particles, ions are constantly being formed at the electrode or grid I2 and current iiows between it and the electrode or plate I I. For a given area of the electrode or plate II and electrode or grid I2, the current density will be a function of the velocity Vp due to the potential maintained between theelectrodes II and I2 and the number of ions formed per second as a result of the .bombardment by the alpha particles It emitted from the radioactive material I'I.

The current density will be a maximum when the velo-city Vg of the gas is zero. It will be reduced as a function of the velo-city of the gas since the greater the gas velocity the more ions will be blown out of the electric field between the electrodes I i and I2, assuming that all other factors remain constant.

In order to measure the current flow between the electrodes II and I2 thermionic measuring means, indicated generally at 20, may be used. The thermionic measuring means 20 may include a pair of electric valves 2I each having an anode 2m, a grid 2 Ig and a hot cathode 2 Ic. The cathodes 2Ic may be interconnected by a resistor 22 whose midpoint is connected through a resistor 23 to ground and to the negative terminal I as shown. The electrode l2 may be connected directly to one of the grids 2Ig and through a resistor 24 to the other 2 Ig which also is connected to a point along a resistor 25, between the terminals I3 and I4, such that the grids 2lg are maintained at a potential of about 65 volts above ground. Y

The thermionic measuring means 2B employs the null method of measurement in that a galvanometer 26 is connected between terminals 27 of anode resistors 28. The resistance of an adjustable resistor 29 is adjusted so that the pointer 33 of the galvanometer 215v occupies a zero position with respect to scale '3| when maximum current flows between the electrodes il and EZ. rihis occurs when the velocity of the gas flow is zero. As the gas ow increases, the ionized molecules l5 are swept out of the space between the electrodes H and l2 proportionally to the gas velocity. The pointer Si)Y moves up the scale 3i a corresponding amount and, accordingly, the scale 3i may be calibrated directly in units of velocity of gas flow as desired.

ySince certain changes can be made in the fore-- going construction and method without departing from the spirit and scope of my invention, it is intended that all matter shown in the accompanying drawing and described herenbefore shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

Apparatus of the, class described comprising, in combination, a first electrode, a second electrode spaced from said first electrode, means for maintaining said electrodes at a predetermined 4 and constant direct current potential, a conduit enclosing said electrodes and disposed for the ow of gas therethrough in a direction substantially transversely of the spacing of said electrodes, and means within said conduit for ionizing the molecules of gas to produce a iiow of ionized molecules from `said first electrodes to said second electrode substantially transversely of the flow of gas through the conduit, said electrodes and ionizing means being arranged so that ionized particles owing from said rst electrode are deiiected so as not to reach said second elecr'ode and inV amount which changes according -to the velocity of the gas ow through said conduit, the means for ionizing the molecules of gas comprising a source of radioactivity and one of the electrodes comprising a grid element disposed between said source of radioactivity and the other electrode.

ALFRED A. OBERMAlE-R.

CITED The foliowing references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,411,796 Meyer Apr. 4, 1922 1,808,799 Blake June 2, 1931 2,442,824 Poyle V June 8, 1948 2,514,235 Genin et al. July 4, 1950 FOREIGN. PATENTS Numb er Country- Date f93,166 Germany Jan. 21, 1927 

